Optical sensor system to identify objects and their movement

ABSTRACT

A system of optical sensors determines whether an object is placed on the system by passing light through the sensor layer, detecting light reflected from the object above the sensor layer, and identifying the object based on whether a color detected in the light corresponds to a color of the side of the object that is positioned on the system over the sensor layer. When the system includes multiple optical sensor units, the system may determine where the object has been placed by determining which of the sensor units detect light reflected from the side of the object.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent document claims priority to and is a continuation of U.S.patent application Ser. No. 16/726,409, filed Dec. 24, 2019, thedisclosure of which is fully incorporated into this document byreference.

BACKGROUND

It is of value to automatically detect and electronically record when anitem is removed from and/or placed on a storage location, such as ashelf. For example, to assist with inventory management and customerengagement, retail store operators desire to identify when a customerremoves a product from a store shelf. It is also useful for retailoperators to know if the product has been returned to the shelf, ormoved to an unexpected location. Warehouse operators, pharmacies,medical and dental service providers and other industries also have akeen interest in identifying when products have been removed from and/orplaced on a storage location.

While inventory control systems currently exist, they typically requirethat the product or its packaging be equipped with a tag, such as aradio frequency identification (RFID) tag that communicates with areceiver that can detect when the tag is within transmission range ofthe receiver. This increases the cost of a product and its packaging,and it also requires the retail store operator (or other storagefacility operator) to coordinate with each product's manufacturer soensure that each product includes a tag that communicates using aprotocol that can be detected and understood by the facility operator'sreceivers. Other inventory control systems require weight sensors and/orcameras with image processing software, each of which can be expensiveand cumbersome to implement.

This document describes a novel method and system that is directed tosolving at least some of the technical problems described above, and/oradditional issues.

SUMMARY

In various embodiments, a system is configured to detect absence orpresence or absence of an object over a substrate. The system includesthe substrate, which includes a sensor layer with one or more sensorunits. The sensor layer includes a first side, along with a second sidethat is opposite the first side. Each sensor unit includes two or moreoptical sensors, at least a first one of which will be aligned with acolor filter of a first color, and at least a second one of whichaligned with a color filter of a second color. Each of the opticalsensors is positioned to detect light that is received through thesecond side of the sensor layer. The system includes a circuit that iselectrically connected to each of the optical sensors and that isconfigured to, when an illumination source directs light into the firstside of the sensor layer, past the optical sensors and through thesecond side of the sensor layer: (i) receive signals from the opticalsensors; and (ii) use the received signals to generate an output thatindicates whether an object of a particular color is placed over thesensor unit.

Optionally, in each sensor unit, a first optical sensor may be alignedwith a red color filter, a second optical sensor may be aligned with ablue color filter, a third optical sensor may be aligned with a greencolor filter, and a fourth optical sensor may be aligned with a white orgray reflecting layer. The optical sensors of each sensor unit may bespaced apart, with transparent or translucent areas between the opticalsensors to permit light from the illumination source to pass between theoptical sensors through the sensor layer.

The substrate also may include a spacer layer positioned along thesecond side of the sensor layer. The spacer layer may have a thicknessthat is equal to or greater than a thickness of the sensor layer.

Optionally, each of the optical sensors may include an amorphous siliconp-i-n photodiode. In addition, each sensor unit may include a transistorthat comprises an amorphous silicon thin film transistor (TFT), a metaloxide semiconductor TFT, a polysilicon thin film transistor, or aprinted organic TFT. Optionally, each sensor unit may includetransistors, each of which includes a first source or drain electrodethat is electrically connected to one of the optical sensors, along witha second source or drain electrode that is electrically connected to anoutput of the sensor unit.

Optionally, the sensor layer also may include a transparent ortranslucent substrate. The sensor layer also may include any number ofmetallic contacts, each of which is positioned between the substrate andone of the optical sensors.

The circuit may include a processor that is electrically connected tooutputs of each of the optical sensors. The system also may include theillumination source, positioned to direct light toward the first side ofthe sensor layer.

During operation, when the object of the particular color is placed onthe sensor unit and the illumination source is active, the illuminationsource will direct light toward a side of the object that exhibits theparticular color. The light that is received through the second side ofthe sensor layer will be, and the optical sensors will detect, lightthat is reflected from the side of the object. The circuit that uses thereceived signals to generate the output that indicates whether or notthe object of a particular color is placed over the sensor unit may thendo so based on whether the optical sensors determine that light of theparticular color has been reflected from the side of the object thatexhibits the particular color.

In some embodiments, the sensor layer may include an array of sensorunits. If so, then the circuit may be electrically connected to each ofthe sensor units. The circuit may, when an illumination source directslight into the first side of the sensor layer, past the optical sensorsand through the second side of the sensor layer, receive signals fromthe optical sensors of each sensor unit. The circuit may then use thereceived signals to generate an output that, for each of the sensorunits: (i) indicates whether an object is placed over that sensor unit;and (ii) when an object is placed over that sensor unit has beendetected, identifies a color of the object that is placed over thesensor unit.

In other embodiments, in a method of detecting presence or absence of anobject of a particular color on a substrate, the substrate is providedto include a sensor layer having a first side, an opposite second side,and one or more sensor units that each include a plurality of opticalsensors. In each sensor unit, at least a first optical sensor is alignedwith a color filter of a first color, and at least a second opticalsensor is aligned with a color filter of a second color. A transparentor translucent area is positioned between the optical sensors. Otheroptional features of the system are discussed in the paragraphs above.When light is passed from the first side of the substrate through thetransparent or translucent area to the second side of the substrate, theoptical sensors will generate signals that are responsive to lightreflected from an object that is positioned over the sensor unit. Acircuit that is electrically connected the optical sensors willreceiving the signals from the optical sensors, analyze the signals toidentify a color in the reflected light, and determine whether the colorin the reflected light corresponds to a particular color. If the colorin the reflected light corresponds to the particular color, the systemwill determine that an object of the particular color is positioned overthe sensor unit on the second side of the substrate; otherwise thesystem will determine that an object of the particular color is notpositioned over the sensor unit on the second side of the substrate. Ifmultiple sensor units are available, the circuit may make thisdetermination for each sensor unit and thus determine which sensorunit(s) have objects of the particular color placed over them.

Optionally, when the system analyzes the signals to identify the colorin the reflected light, the system may determine whether the signalreceived from each of the optical sensors is low or high, and thendetermine the color of the reflected light as a color that correspondsto a combination of the color filters that are aligned with opticalsensors that have emitted a high signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example sensor unit that includes a set of opticalsensors.

FIG. 2 illustrates an example system that may be installed in a storagestructure for sensing the presence of an object on the storagestructure.

FIG. 3 illustrates a system that includes multiple storage structuresthat are in communication with a remote processor.

FIG. 4 illustrates an example matrix addressing arrangement.

FIG. 5 illustrates a system that may address and read outputs frommultiple sensor units.

FIG. 6 illustrates an example arrangement of four sensor units in asensor layer, with corresponding electrical connections.

FIG. 7 illustrates an example photodiode structure.

DETAILED DESCRIPTION

As used in this document, the singular forms “a,” “an,” and “the”include plural references unless the context clearly dictates otherwise.Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of ordinary skillin the art. As used in this document, the term “comprising” (or“comprises”) means “including (or includes), but not limited to.” Whenused in this document, the term “exemplary” is intended to mean “by wayof example” and is not intended to indicate that a particular exemplaryitem is preferred or required.

In this document, when terms such “first” and “second” are used tomodify a noun, such use is simply intended to distinguish one item fromanother, and is not intended to require a sequential order unlessspecifically stated. The term “approximately,” when used in connectionwith a numeric value, is intended to include values that are close to,but not exactly, the number. For example, in some embodiments, the term“approximately” may include values that are within +/−10 percent of thevalue.

In this document, the term “connected”, when referring to two physicalstructures, means that the two physical structures touch each other.Devices that are connected may be secured to each other, or they maysimply touch each other and not be secured.

When used in this document, terms such as “top” and “bottom,” “upper”and “lower”, or “front” and “rear,” are not intended to have absoluteorientations but are instead intended to describe relative positions ofvarious components with respect to each other. For example, a firstcomponent may be an “upper” component and a second component may be a“lower” component when a device of which the components are a part isoriented in a first direction. The relative orientations of thecomponents may be reversed, or the components may be on the same plane,if the orientation of the structure that contains the components ischanged. The claims are intended to include all orientations of a devicecontaining such components.

Additional terms that are relevant to this disclosure will be defined atthe end of this Detailed Description section.

This document describes a system that is able to detect when a producthas been placed on or removed from a particular location on a shelf orother storage structure. In this document, we will use the term “shelf”by way of example as a storage structure. However, the system also maybe implemented for other storage structures such as drawers, walls onwhich items (such as pictures) are hung, floors on which products areplaced, and other physical structures on or against with a product maybe placed. In addition, this description may use location-descriptiveterms such as “on”, “over” or “under” to refer to relative locationswith respect to a storage structure. When the structure is a horizontalstructure such as a shelf or floor, then terms such as “on” and “over”will mean that the item is positioned on or over the structure, and“under” will mean under the structure. However, when the structure is awall or other vertical structure against which the item is placed, then“on” or “over” refers to a side of the structure against which the itemrests, while “under” refers to the opposite side of the structure.

The system includes a set of optical sensors that are arranged in anarray or other arrangement and positioned on or in the shelf, wall,floor or other storage structure. Each product is positioned over asensor unit, and the system may include an array of sensor units, eachof which is positioned on a location that corresponds to the expectedlocation of a product when placed on the structure. When a product isplaced on the shelf over the sensor unit, light will pass through theshelf to the product, and reflect back on the sensor unit. If no productis on the shelf, then light will not reflect back to the sensor unit butinstead the sensor unit will only detect ambient light above the shelf.The sensor unit will then generate a signal that indicates the color ofthe product (if any) that is positioned over the sensor unit over theshelf. A processor may analyze this signal to determine whether thedetected color matches an expected color of a product that is to beplaced on the shelf.

The examples below will show products having similar sizes and aparticular bottom shape. However, the system can accommodate othersituations with a variety of sized and shaped products.

FIG. 1 illustrates an example of a sensor unit 100 having a set ofoptical sensors 101-104. At least a two of the optical sensors will bealigned with color filters so that a color filter is positioned overeach of the sensors. For example, in the sensor unit 100 shown in FIG.1, the first optical sensor 101 may be aligned with a red color filter.The second optical sensor 102 may be aligned with a blue color filter.The third optical sensor 103 may be aligned with a green color filter.The fourth optical sensor 104 may be aligned with a white, gray or nocolor filter. Other colors, and fewer or more optical sensors, may beused in various embodiments, although the use of primary colors red,green and blue in the filters is desirable for applications in which avariety of colors must be detected as it renders the sensor unit usefulfor identifying a wide variety of reflected colors across the colorspectrum. In addition, while the sensor unit shows the sensorspositioned in a 2×2 array, other arrangements are possible so long asthe sensors are spaced far enough apart from each other to permit lightto pass between the optical sensors to a spacer layer as will bedescribed below. Optionally, the sensor unit also may include one ormore additional optical sensors that are configured to measureillumination intensity, as will be described below in the discussion ofFIG. 2.

FIG. 2 illustrates an example system for detecting the presence orabsence of an object on a storage structure. In FIG. 2, the object 201is placed on a shelf 202. The shelf 202 includes a sensor layer 203containing one or more sensor units, each of which is positioned underan expected object location. In FIG. 2, the expected object location isdenoted by the space between location guides 232, which may be featuressuch as one or more sidewalls, printed markings on the shelf, guidewires or other structures or markings that will assist a user indetermining where to place the object 201 on the shelf 202. However, thelocation guides 232 are optional and are not a requirement of thesystem. The shelf 202 also includes a spacer layer 204 that ispositioned along a first side (i.e., over) the sensor layer 203, betweenthe sensor layer 203 and the shelf face on which the object 201 isplaced. The system also includes an illumination source 209 that ispositioned along (e.g., under) a second side of the spacer layer 203. Asshown in FIG. 2, the side of the spacer layer 203 along which theillumination source is positioned is opposite the side of the spacerlayer 203 along which the spacer layer 204 is positioned.

Each sensor unit includes two or more optical sensors 213, 214. Althoughonly two of the optical sensors are shown in FIG. 2, the example sensorunit may include another number of optical sensors (as the four sensorembodiment of FIG. 1, arranged in a 2×2 array). Any or all of theoptical sensors 213, 214 may be aligned with a color filter 215, 216 sothat each color filter is positioned over a corresponding opticalsensor. In the example shown, optical sensor 213 is aligned with colorfilter 215, while optical sensor 214 is aligned with color filter 216.The color filters 215, 216 may be positioned in the spacer layer 204 asshown in FIG. 2, or alternatively they may be positioned over theircorresponding optical sensors 213, 214 in the sensor layer 203.

Each of the sensor layer 203 and the spacer layer 204 will betransparent or translucent so that light from the illumination source209 may pass through the layers (and past the optical sensors of thesensor layer), reflect off of the underside of the object 201, and bedirected back to the optical sensors 213, 214. The sensor layer 203 andthe spacer layer 204 may be comprised of different materials or of acommon material, and they may be two separate layers or a single layeras shown. For example, the spacer layer 204 may be formed of a clearplastic material, having a thickness that is at least as large as thethickness of the optical sensors (such as approximately 1 mm toapproximately 2 mm). Optionally, in some embodiments, the sensor layer203 may simply include the sensor units, attached to or positioned underthe bottom of the spacer layer 204 with no other supporting structure.The optical sensors 213, 214 of each sensor unit will be spaced apartfrom each other so that light from the illumination source 209 may passbetween the optical sensors to the spacer layer 204.

In operation, light from illumination source 209 will pass into thefirst side of the sensor layer 203, out the second side of the sensorlayer 203, and through the spacer layer 204 if present. The opticalsensors 213, 214 of the sensor unit will detect light received fromabove the shelf 202 and each generate a signal having characteristicsthat a processor can use to determine the color of an object (if any)that is positioned over the shelf. The light detected by the opticalsensors 213, 214 may be light that originated from the illuminationsource that passed through the sensor layer 203 and returned to thesensor layer 203 after reflecting off of the object 201. Or, if noobject is over the sensor unit, the optical sensors 213, 214 may detectambient light or no light. For example, if a first optical sensor 214 isaligned with a green filter 216 and a second optical sensor 213 isaligned with a blue filter 215, then the signal emitted by the firstoptical sensor 214 will be active (i.e. reflected light will bedetected) and the signal emitted by the second optical sensor 213 willbe inactive (i.e. no reflected light) when a green object is placed onthe shelf. When the green object is removed from the shelf, the activityof the sensors will change, allowing the system to determine that thegreen object has been removed. For example, when the green object isremoved from the shelf the optical sensors 213, 214 will no longerprovide signals corresponding to the green reflected light. Instead thesensors become exposed to ambient light and their signals willcorrespond to this different illumination. The changes in the sensorsignals allow the system to determine that the object is removed.

The sensor unit also may include an additional optical sensor 218 thatis aligned with a white reflector 217. The additional optical sensor 218may serve as a calibration sensor to measure the intensity of theillumination.

The illumination source 209 may be any suitable light source, such asone or more light emitting diodes, a halogen or other type light bulbthat emits white light, or even ambient light of the facility in whichthe storage structure is located.

FIG. 3 illustrates that a facility with multiple shelves 301 (or otherstorage structures) may include multiple sensor units 302. In fact, eachindividual shelf may include multiple sensor units 302. The opticalsensors of each sensor unit will be electrically connected via wires,conductive traces, or other conductive structures to a circuit that isconfigured to receive the signals from the optical sensors, determinethe color that the optical sensors are detecting, and generate an outputthat indicates whether or not an object is positioned over the sensors.If the color detected by any sensor unit matches an expected color, thesystem will determine that the object is positioned over the sensorunit. If not, the system will determine that the object is not locatedat the position. The circuit may include one or more components that areintegral with the storage structure, and optionally one or morecomponents that are located remotely from the storage structure but incommunication with components in the storage structure. For example, thestorage structure may include an integral processor 305 that performsthe detection and determination functions. The processor may be, forexample, a microprocessor or a component of a microcontroller.Alternatively or additionally, the circuit may include a transmitter 306by which the storage structure will transmit the sensors” output and/orthe processor's output to a remote processor 307, such as a local orcloud-based server, either directly or via communication paths along oneor more communication networks 308.

The local processor 305 or remote processor 307 may continuously monitorthe sensor readout from optical sensors. Alternatively, the processormay initiate monitoring on a periodic basis, or in response to atriggering action such as a command or request to provide informationabout a shelf's contents. The processor may combine the response fromthe optical sensors to determine the color on the base of the product.The system may then access a data store 310 of stored inventoryinformation to determine, based on one or more criteria such as timeand/or location, a color of the product that is expected to be locatedon the shelf at the current time. If the color expected matches thecolor that is detected, the processor may return an indication that theexpected product is on the shelf, above the sensor unit. If the expectedcolor is not detected, the processor may return an indication that theexpected product is not at its expected location.

In various embodiments, the optical sensors may be any photosensitivesensing devices. For example, the sensors may be photodiodes, such asamorphous silicon (A-Si) p-i-n (PIN) photodiodes. A-Si photodiodes aresensitive across the visible spectrum and have wide dynamic range, whichcan be valuable attributes for the device.

Each photodiode of each sensor unit may be electrically connected to anaddressing transistor, and addressed using a matrix addressingarrangement such as is known in the art. For example, referring to FIG.4, the n column of each photodiode 401-404 may be connected to the gateof a corresponding thin film transistor (TFT) 415-418. For eachtransistor (e.g, 415), one of the TFT's source-drain electrodes iselectrically connected to a photodiode (e.g., 401) and the other of theTFT's source-drain electrodes is electrically connected to acorresponding output 421-424. In various embodiments, the transistorsmay be fabricated from amorphous silicon, polysilicon, printed organic,metal oxide or other semiconductors. Other addressing arrangements suchas direct addressing of each photodiode by the microcontroller may beused.

The photodiodes 401-404 may have a reverse bias voltage such as 0-5volts. A gate addressing line 431 is used so that the signal of eachphotodiode is read out by addressing each gate line in sequence with avoltage pulse to turn the gate on (such as approximately 10 toapproximately 20 volts), while the other gate lines are turned off(typically approximately 0 to approximately −5 volts.

For multiple sensor units, such as the 5×5 array of sensor units 501shown in FIG. 5, the gate addressing sequence could be accomplished witha shift register 502, or by individual contacts of a microprocessorcontroller so long as the number of gates does not exceed the number ofavailable contacts of the microprocessor. Similarly, the outputs couldbe selected by a multiplexer 503, or by individual contacts to acontroller. The gate pulse length could be chosen to read out the entirearray in a designated time, such as a time that is the product of thenumber of gates and the gate pulse period.

FIG. 6 illustrates an example sensor layer that includes of a group offour sensor units 601-604, each of which includes four photodiodes, andtheir corresponding electrical interconnects. Translucent or transparentareas 612, denoted by the white spaces within the crosshatched areas inFIG. 6, enable light to pass through the sensor layer to reflect off ofthe placed object. Optional opaque areas 611, denoted by thecrosshatched areas in FIG. 6, prevent illumination where it is notrequired. FIG. 7 illustrates how a photodiode 713 of the sensor layer703 may be fabricated with an opaque metallic bottom contact 720, whichin turn rests on a substrate 722 x. The opaque contact prevents theillumination source 609 from directly illuminating the sensor throughthe bottom contact. Instead light from the illumination source 709reflects off the bottom of the object 701, through the spacer layer 704and filter 715, where light corresponding to the color of the filterwill reach the photodiode 713.

When red, green and blue (R, G, B) filtered optical sensors are used,the three color sensors generate signals corresponding to the reflectionof light from the base of the product. The signal can be normalized tothe signal from the fourth photodiode which is reflected off the white(or grey) reflector. The color detected may correspond to a combinationof the color filters that are aligned with optical sensors that haveemitted a high signal. As a simple example with a 1-bit signal, if theoptical sensor that is aligned with a red filter emits a high signalwhile the other filters emit a low signal or no signal, the system maydetermine that the color of the light (and thus the color of the objectabove the sensor unit) is red. If the optical sensors having blue andred filters emit high signals, the system may determine that an objectpositioned above the sensor unit is purple. Optionally, the reflectormay scatter light rather than provide specular reflection. The signalscan be calibrated by measurement of a white, black and/or other colorbase. Thus, the system can detect the color of an object based over thesensor unit based on the color of reflected light, as detected by theeach of the color-filtered optical sensors.

The number of unique colors that the system can detect may vary based onthe signal-to-noise of the sensor output and the recording electronics.For example, a 1-bit signal, in which the controller determines whetherthe individual photodiode signals are low or high (zero or 100%) asdescribed in the example of the previous paragraph, can identify 8unique colors. The R, G and B signals will have output values such as(1, 1, 0) or (0, 1, 0) to represent the colors. A 2-bit signal canidentify 16 unique colors and requires a 3 level measurement resolution(0, 50% and 100%), giving color representations such as (1, 0.5, 0), andso on for higher resolutions.

The ability to sense multiple colors allows the type of objects placedon the shelf to be identified. One side of each object, typically thebase, may be colored such that objects of the same type have the samecolor and objects of a different type have a different color. The colorsare selected to have known components of red, green and blue, as isknown in the art, so that the output values of the sensors in a sensorunit can identify the color. The microcontroller unit that operates thesystem can contain the correspondence between color and object type, andhence the object type can be identified. The system can thereforedetermine the presence or absence of an object at a specific location onthe sensor array, and if an object is present the system can determinethe object's type.

The system may scan the sensor array repeatedly at a designated repeatfrequency, or in response to commands to scan the array, and record thedata from all the sensor units. The signals generated by the photodiodesmay be interpreted by a computing system such as a microprocessorcontroller unit that has a central processing unit (CPU), memory andinput/output channels. The input channels may need analog-to-digitalconverters to convert the analog output signal of sensor to a digitalinput signal for the CPU. The controller may use the data to identifyall the products that positioned over the sensor units using apreviously established data set of colors, and the data will showwhether an item of an expected color has been removed since the previousarray scan. The data can be arranged to be displayed on a screen or ifan object has been picked up, pre-determined relevant information can bedisplayed for a user. The data can also be transmitted is suitable forman external system for analysis.

While the examples shown and discussed in this Detailed Description usethe example of a product placed on a shelf as in a retail store, it isto be understood that the disclosed embodiments can be applied to anylocation where it is desirable to monitor whether an object is absent orpresent on a storage structure. For example, the system may beincorporated into storage structures such as display cases, pharmacyshelves, storage drawers, tool carriers, medical equipment cards, wallsthat display artwork, floors of vehicle parking facilities, and a widevariety of other locations.

Terminology that is relevant to this disclosure includes:

The terms “processor” and “processing device” refer to a hardwarecomponent of an electronic device that is configured to executeprogramming instructions. Except where specifically stated otherwise,the singular terms “processor” and “processing device” are intended toinclude both single-processing device embodiments and embodiments inwhich multiple processing devices together or collectively perform aprocess.

The terms “memory,” “memory device,” “data store,” “data storagefacility” and the like each refer to a non-transitory device on whichcomputer-readable data, programming instructions or both are stored.Except where specifically stated otherwise, the terms “memory,” “memorydevice,” “data store,” “data storage facility” and the like are intendedto include single device embodiments, embodiments in which multiplememory devices together or collectively store a set of data orinstructions, as well as individual sectors within such devices.

In this document, the terms “communication link” and “communicationpath” mean a wired or wireless path via which a first device sendscommunication signals to and/or receives communication signals from oneor more other devices. Devices are “communicatively connected” if thedevices are able to send and/or receive data via a communication link.“Electronic communication” refers to the transmission of data via one ormore signals between two or more electronic devices, whether through awired or wireless network, and whether directly or indirectly via one ormore intermediary devices.

In this document, the term “imaging device” refers generally to ahardware sensor that is configured to acquire digital images. An imagingdevice may capture still and/or video images, and optionally may be usedfor other imagery-related applications. For example, an imaging devicecan be held by a user such as a DSLR (digital single lens reflex)camera, cell phone camera, or video camera. The imaging device may bepart of an image capturing system that includes other hardwarecomponents. For example, an imaging device can be mounted on anaccessory such as a monopod or tripod. The imaging device can also bemounted on a transporting vehicle such as an aerial drone, a roboticvehicle, or on a piloted aircraft such as a plane or helicopter having atransceiver that can send captured digital images to, and receivecommands from, other components of the system.

The features and functions described above, as well as alternatives, maybe combined into many other different systems or applications. Variousalternatives, modifications, variations or improvements may be made bythose skilled in the art, each of which is also intended to beencompassed by the disclosed embodiments.

1. A system for detecting presence or absence of an object, the systemcomprising: one or more sensor units, each of which comprises aplurality of optical sensors, wherein each of the optical sensors ispositioned to detect light that is directed from an illumination source;and a circuit that is electrically connected to each of the opticalsensors and that is configured to, when the illumination source directslight into the plurality of optical sensors: receive signals from eachof the plurality of optical sensors, use the received signals from eachof the plurality of optical sensors to generate an output that indicatesa color, wherein the color correlates to a surface color of an object;and the color corresponds to a predetermined surface color, determinethat the object is placed over the sensor unit, otherwise not determinethat the object is placed over the sensor unit.
 2. The system of claim1, wherein the optical sensors include a calibration sensor configuredto measure an intensity of the light.
 3. The system of claim 1, whereinthe optical sensors are spaced apart with transparent or translucentareas between the optical sensors to permit light from the illuminationsource to pass between the optical sensors through the sensor layer. 4.The system of claim 1, wherein each of the optical sensors comprises anamorphous silicon p-i-n photodiode.
 5. The system of claim 1, whereineach sensor unit further comprises a transistor that comprises: anamorphous silicon thin film transistor (TFT); a metal oxidesemiconductor TFT; a polysilicon thin film transistor; or a printedorganic TFT.
 6. The system of claim 1, further comprising: a transparentor translucent substrate; and a plurality of opaque metallic contacts,each of which is positioned between the substrate and one of the opticalsensors.
 7. The system of claim 1, wherein each sensor unit comprises aplurality of transistors, each of which comprises: a first source ordrain electrode that is electrically connected to one of the opticalsensors; and a second source or drain electrode that is electricallyconnected to an output of the sensor unit.
 8. The system of claim 1,wherein the circuit comprises a processor that is electrically connectedto outputs of each of the optical sensors.
 9. The system of claim 1,further comprising the illumination source.
 10. The system of claim 1,wherein, during operation, when the object of the particular color isplaced on the sensor unit, the circuit that uses the received signals togenerate the output that indicates the color will do so based on whetherthe optical sensors determine that light of the particular color hasbeen reflected from the side of the object that exhibits the particularcolor.
 11. A system for detecting and identifying objects, the systemcomprising: a plurality of optical sensors positioned to detect lightthat is directed from an illumination source, wherein the opticalsensors are spaced apart to permit light from the illumination source topass between the optical sensors; and a circuit that is electricallyconnected to each of the optical sensors and that is configured to, whenthe illumination source directs light into the plurality of opticalsensors: receive signals from each of the plurality of optical sensors,use the received signals to generate an output that indicates a color,wherein the color correlates to a surface color of an object, and if thecolor corresponds to a predetermined surface color, determine that theobject is placed over one or more of the optical sensors, otherwisedetermine that the object is not placed over one or more of the opticalsensors.
 12. The system of claim 11, wherein the optical sensors includea calibration sensor configured to measure an intensity of the light.13. The system of claim 11, wherein each of the optical sensorscomprises an amorphous silicon p-i-n photodiode; and further comprising:one or more transistors coupled to each of the plurality of opticalsensors, wherein each of the one or more transistors comprises: anamorphous silicon thin film transistor (TFT), a metal oxidesemiconductor TFT, a polysilicon TFT, or a printed organic TFT.
 14. Thesystem of claim 11, further comprising: a transparent or translucentsubstrate; and a plurality of opaque metallic contacts, each of which ispositioned between the substrate and one of the optical sensors.
 15. Thesystem of claim 11, further comprising one or more transistors coupledto each of the plurality of optical sensors, wherein each of the one ormore transistors comprises: a first source or drain electrode that iselectrically connected to one of the optical sensors; and a secondsource or drain electrode that is electrically connected to an output ofone or more of the plurality of optical sensors.
 16. The system of claim11, further comprising the illumination source.
 17. The system of claim11, wherein, during operation: the optical sensors will determinewhether light has been reflected from the side of an object that hasbeen placed over one or more of the plurality of optical sensors; andfor any optical sensors over which an object has been placed, theoptical sensors will detect light reflected from the object, and thereceived signals will identify the color of the object based on color ofthe light reflected from the object.
 18. A method of detecting presenceor absence of an object of a particular color on a substrate, the methodcomprising: providing a substrate that includes a sensor layercomprising: a first side and an opposite second side, a sensor unit thatcomprises a plurality of optical sensors, and a transparent ortranslucent area between the optical sensors; passing light from thefirst side of the substrate to the second side of the substrate; by theoptical sensors, generating signals that are responsive to lightreflected from an object that is positioned over the sensor unit; and bya circuit that is electrically connected the optical sensors: receivingthe signals from each of the plurality of optical sensors, analyzing thesignals to identify a color in the reflected light, the color beingdetermined using the signals from each of the plurality of opticalsensors and correlating to a surface color of an object, determiningwhether the color in the reflected light corresponds to a predeterminedsurface color, and in response to the color in the reflected lightcorresponding to the predetermined surface color, determining that anobject of the particular color is positioned over the sensor unit. 19.The method of claim 18, wherein analyzing the signals to identify thecolor in the reflected light comprises determining whether the signalreceived from each of the optical sensors is low or high, and thendetermining the color of the reflected light.
 20. The method of claim18, wherein: the substrate further comprises a spacer layer that forms asecond side of the substrate; and passing the light from the first sideof the substrate to the second side of the substrate further comprisespassing the light through the spacer layer.